1242

THE COLLIERY GUARDIAN.

June 5, 1914.

immersed type. The transformers are fitted with the
Merz-Price patent protective system, so arranged that
the low-tension board is cleared in the case of a failure
of the high-tension supply, in addition to a breakdown
in the transformers themselves.

The low-tension board consists of the two transformer
panels and four feeder panels, and controls the supply
to the screens and workshops, and other motors on the
surface.

Air Compressors.—Two motor-driven air compressors
are installed in the power house. The compressors are
made by Messrs. Beiliss and Morcom Limited, and the
motors and starting gear by the British Westinghouse
Electric and Manufacturing Company Limited. The
compressors are of the vertical high-speed forced lubri-
cation type, running at 233 revolutions per minute, and
fitted with Rogler-FIoerbiger suction and delivery valves.
These valves are quite noiseless in action, and, so far,
have given complete satisfaction. An automatic adjust-
able unloading valve is fitted on the air inlet, and so
arranged that on the pressure at the delivery exceeding
the normal by from 3 to 5 lb. per square inch, the valve
closes and shuts off the air supply. The valve can also
be permanently closed by a lever. The capacity of each
compressor is 3,000 cu. ft. of free air per minute, com-
pressed to 80 ]b. per square inch. The compressor is of
the two-stage type, fitted with an intercooler. The two
cylinders are 33 and 19 in. in diameter respectively, and
the stroke is 15 in. The number of cubic feet of free
air compressed to 80 lb. per square inch per brake horse
power is 5*75. The amount of cooling water required
for the water jackets and intercooler is 4,500 gallons per
hour per compressor. The motors are of 535-brake horse
power each, and are supplied with current at a pressure
of 2,900 volts. They are of the slip-ring type, and are
started by liquid starting switches.

Fans and Fan Motors. — Two Walker fans, motor-
driven by means of ropes and rope pulleys, are
installed, one capable of delivering 250,000 cu. ft. per
minute at 4 in. of water gauge, and the other 400,000
cu. ft. per minute at 8 in. of water gauge, the full
speeds being 185 and 215 revolutions per minute respec-
tively. The brake horse power necessary to drive these
fans at their full capacity are 300 and 800 respectively.
During the development of the colliery the fans will be
run at varying speeds by changing the rope pulleys. At
the present time the small fan is operated by a motor
of 100-brake horse power, and the large fan by a 300-
brake horse power motor. Later on the 300-brake horse
power motor will be used for the small fan, and a bigger
motor of 800-brake horse power will be installed to drive
the large fan, the 100-brake horse power motor being
then used for haulage purposes underground.

Motor Generators.—For the lighting of the colliery,
both at bank and round the bottom of the shaft, two
motor generators have been installed. Each has a
capacity of 60 kilowatts, delivering direct current at 220
volts, and both are driven from the high-tension board.
It was decided to instal motor generators and direct
current lighting in order to prevent any fluctuation of
the supply voltage when the winders are running from
affecting the lighting circuit. Provision is made for the
installation of a further set as the lighting load increases.

These machines also supply the current for the house
and street lighting in the recently constructed village at
the colliery. Each row of houses is provided wTith a
pair of service cables, running its full length in the false
roof, to which cables the individual houses are connected.
The ends of the service cables are brought out at the
ends of the rows, and are there connected to the main
bare stranded copper distributors, which connect the
rows together. The systematic lay-out of the village
lends itself to this treatment, and the whole installa-
tion has, in consequence, a very neat appearance. No
meters are installed in the houses, but each consumer
pays a weekly amount according to the number of
lamps installed. The street lighting is carried out by
lamps attached either to steel poles in the case of the
main streets, or to wall brackets in the less important
streets. In the latter case, the distributors are carried
along the chimney stacks, and the lamps themselves
are coupled up by means of twin lead covered cable.

Pumping Plant.—The permanent pumping plant to
be installed in the Low Main seam will consist of three
motor-driven high-lift turbine pumps, each capable of
pumping 1,500 gallons of water against a 1,020 ft. head,
including pipe friction. The pumps are being con-
structed by Messrs. Sulzer Brothers, of Winterthur
(Switzerland), and the motors and starters by the British
Westinghouse Electric and Manufacturing Company
Limited. The designed speed of the . pumps is 1,170
revolutions per minute.

The general lay-out of the underground pump-room,
which also contains the main distributing switchboard
for the Low Main seams, is shown in figs. 16 to 18.
Duplicate delivery mains, each 15 in. in diameter, are
carried up the shaft, and the valves are so arranged that
the pumps can discharge into either delivery main. The
motors are supplied with current at a pressure of 2,800
volts, and starters of the liquid type. The guaranteed
efficiency of the combination of pump and motor from
the electrical horse power input to the horse power in
the water pumped is 71'6 per cent.

Tenders were obtained for ram pumps when the
pumping scheme was first under consideration, as it
was thought that, owing to the higher efficiency of the
ram pump, it might be advisable (seeing that the energy
has to be purchased) to use ram pumps for . ordinary
working, with a centrifugal pump stand-by. It was
found, however, that although the efficiency of the best
type of duplex ram pump combination was 80 per cent.,
as against 71’6 per cent, for the centrifugal combination
described above (producing a saving in the current bill of
.£400 per annum), the capital cost of the former was
nearly 24 times that of the latter, making the total
costs per annum, when capital charges were included,

slightly less with the centrifugal combination. This
estimate did not take into account the cost of the larger
pump room required for the ram pump scheme, and the
extra cost of running and upkeep which would
undoubtedly be incurred in the case of ram pumps. If
the price paid for electric energy had been much greater
than it is in this case, however, the extra cost of ram
pumps would have been justified.

Smalt Surface Motors.—Motors under 50-horse power
used for the various services at the surface are supplied
from tlie low-tension switchboard previously mentioned,
and are divided into three circuits. The first circuit
includes one 20 and one 40-horse power motor, driving
the machine shop shafting and the circular sawT respec-
tively. The staple pit pump motor of 20-horse power,
which will be increased later to 60-horse power, is on a
second circuit, while the third feeds the whole of the
motors which drive the screening plant. A fourth cir-
cuit is provided for, winch will eventually be used for
small surface haulage motors. The motors are either
of the protected or of the totally enclosed pipe ventilated
type, and are controlled by switches, fuses, and starters
combined in single units. The motors driving the
screening plant are as follow :—

Screens ............ Two of 40-h.p., squirrel-cage type.

Picking be’ts ...... Four of 20-h.p., slip-ring type.

Jib-loading gear.... One20-h.p.,	,,	„

Marcus screen....... One 20-h.p ,	„	„

A separate house has been provided for the 40-horse
power screen motors, which are of the protected type,
and similar to the saw motor.

The picking belt motors and loading jib motor, which
of necessity are totally enclosed, are arranged for pipe
ventilation, by which means their dimensions have been
kept down to those of the 20-horse power protected
motors in the workshop and staple pit, thus making the
parts of the whole of these motors interchangeable. The
air inlets of these pipe ventilated motors are connected
to a common inlet pipe, which is taken outside the
heapstead building, in order to obtain clean air for
ventilation.

Underground Haulages.—Endless rope haulages in
the main roads of each seam are projected, each driven
by a 100-horse power three-phase motor, operated direct
at 2,800 volts. The motors will be of the slip-ring type,

The Geology of the Kent Coalfield.

By E. A. NEWELL ARBER, M.A., Sc.D., F.G.S., Trinity College, Cambridge,
University Demonstrator in Palaeobotany.

From a paper read before the Institution of Mining Engineers, London, June 4, 1914.

Introduction.

In this paper the writer has attempted to give a
general account of the geology of the concealed coalfield
of East Kent, so far as there appears to him to be
sufficient evidence available. In so doing he has
endeavoured to adopt a non-committal attitude in
regard to many points on which the available data are
not as yet as conclusive as one could wish. Much
further exploration is undoubtedly necessary before the
full structure of the coalfield is disclosed. It may
even be that some of the conclusions expressed here,
which, to the writer at least, appear to be now well
founded, may eventually require some revision in the
light of the results of further discoveries. This is
particularly the case as regards the sketch map (fig. 1).
The exact position of almost all the outcrops and boun-
daries, and the form of all curves shown thereon are
unknown at present, and thus the lines indicated on the
map are only roughly approximate as regards relative
position. The writer has here ignored completely the
overlying mesozoic rocks. k special study of these
beds has been already published by the Geological
Survey, who have also in progress the examination of
more recently acquired evidence. He is, therefore,
concerned solely with the carboniferous rocks.

The author then proceeds to give a historical survey
of Lie whole question.

The Evidence.

In this contribution to our knowledge of the geological
structure of the Kent coalfield, the writer has made use
of all the evidence known to him. Some of this infor-
mation has been already published, especially the
records of the Shakespeare Cliff, Ropersole, Ellinge,
Waldershare, Fredville, and Ebbsfleet borings, as well
as of others which lie off the coalfield. The vertical
sections of 10 further borings of, in most cases, more
recent date have been given in outline by Dr. Malcolm
Burr* recently in the Colliery Guardian, in which will
be found details of these borings.

(a) The Central Borings and Sinkings.—For reasons
which will be discussed more fully at a later stage, the
writer is inclined to think that the Waldershare boring
is situated near the centre of the field. With it may
be associated the Fredville boring and Snowdown sink-
ing (which are within a few yards of one another),
rather more than 2| miles to the north-west of Walder-
share. The important Barfreston boring is situated 1|

* The Deep Borings in East Kent, Colliery Guardian,

October 10, 1913.

and fitted with oil-immersed controllers. This part of
the work, however, has not yet been installed.

Cables.—The whole of the cables on the installation
are paper insulated, lead covered, .and wire armoured,
with the exception of the surface lighting cables, which
are carried overhead, and the power cables inbye, which
are paper insulated, bitumen sheathed, and double wire
armoured. The cables feeding the winding engines,
workshops, and screens, and the portion of the shaft
cables that runs between the switchboard and the shaft,
are single wire armoured,- while the shaft cables them-
selves are double wire armoured. All the cables on the
surface are laid in sand, in specially built brick trenches.
At the shaft head the trench in which the shaft cables
are laid is enlarged into a chamber, in which a joint box
connects the surface portions of the cables to the shaft
cables proper. The two power shaft cables, each, of
0’25 sq. in. section, and carrying current at a pressure
of 2,900 volts, connect the switchboard in the pump
house in the Low Main seam at a depth of 356 yds. with
that in the power house at bank, being looped into the
switchboard in the Five-quarter seam en route. One
cable is continued down to the Hutton seam, but is
reduced in section to 0’05 sq. in.

The power switchboards in the three seams are com-
posed of standard cast iron panels of the mining type,
having the busbars run in solid with, compound, and
carrying protective gear for the incoming and outgoing
cables, which, in the case of the shaft cables, is time-
limit overload.protection, and standard core balancing
in. the case of the inbye haulage cables. This type of pro-
tection permits of each cable being immediately isolated
in the case of leakage to earth anywhere on its circuit,
and this is effected without the provision of any pilot
wires.

In order to prevent the pumping and haulage load
from affecting the steadiness of the lighting pressure,
and also to ensure continuance of the lighting supply
in case of the tripping out of the power feeders, a
separate lighting cable is run from the direct current
switchboard in the power house to a distribution board
in the Hutton seam, being looped into the Five-quarter
and Low Main seams in the same way as the power
feeders.

In conclusion, it may be stated that, so far as the
work has at present, gone, the results have justified the
installation of electrically-driven plant throughout.

miles north-north-west, and the Tilmanstone sinking 1|
miles north-north-east of Waldershare. The Ropersole
boring lies some distance west of Waldershare. These
borings and sinkings form a natural group on the palseo-
botanical evidence.

(5) TheNorthern Borings.—A very important group of
borings has been put down in the northern part of the
field, of which the southernmost is that of Goodnestone,
which is also centrally situated. The Goodnestone
boring lies 2| miles almost due north of the Barfreston
boring. About three miles nearly due north of Good-
nestone lies the Walmestone boring. Between the
latitudes of these two borings there is, on the east, the
Woodnesborough boring, lying about 24 miles north-east
of Goodnestone, and the Mattice Hill (Sandwich)
boring, nearly five miles distant, and situated a little
more to the east. On the north-west the Trapham
(Wingham) boring is distant less than 2| miles. There
are two further borings, situated north.of the. Walme-
stone boring. Of these, Stodmarsh boring is less than
2J miles distant north-west-west, and the Ebbsfleet
boring, belonging to the Ebbsfleet syndicate, lies about
six miles north-east of Goodnestone. There are also
several other borings north of the Stour belonging to yet
another company, but concerning these the writer
possesses no information.

(F The Eastern Borings.—The writer turns next to an
important group of three borings lying to the east of the
central region of the coalfield. Of these, Maydensole is
situated 2| miles slightly south of east of Waldershare,
and Oxney 2| miles still further east, along practically
the same line. Lastly, there is the Ripple boring, lying
4{- miles north-north-east of Waldershare, and about two
miles to the north of Oxney. A comparative study of
the fossil floras of these three borings has brought out
the interesting fact that the transition coal measures
thin rapidly to the east of Waldershare. At Mayden-
sole, the westernmost of the three borings, they are
about 1,156 ft. thick, at Ripple 518 ft., and on the east
at Oxney 778 ft. thick.

The Form of the Basin and its Boundaries.

The writer conceives the form of the Kent coalfield to
be a basin-shaped syncline, suddenly truncated on the
west, and occupying the western flank of an anticline
trending more or less north and south beneath the
Straits of Dover. The central and northern regions
underlie land, and the southern and eastern portions
underlie the English Channel and the Straits of Dover.
The basin appears to be one of considerable size, or at
least this is the view which may at present be adopted
provisionally.

The northern boundary is now fairly completely
located, although the exact form of the curve has yet
to be determined. The Ebbsfleet boring is situated
immediately south of the concealed outcrop of the
carboniferous limestone; and other borings, north of the
river Stour, have indicated clearly the position of the